Trouble connecting to rpi after upgrading to oh3

hello all,
i have openhabian installed on a rpi3 and after migrating to oh3 i cannot access the rpi.
right now its connected via a lan cable. i can access it tho via putty and i can enter the configuration via openhabian-config. i also canceled the wireless connection in the wireless section couse was saying that your system has a WiFi interface that fails to initialize on installation…
if i enter the system settings and try to activate the wifi it say:

There was an error or interruption during the execution of:
"30 | System Settings"       
Please try again. If the error persists, please read                         │
/opt/openhabian/docs/openhabian-DEBUG.md or                                  │
https://github.com/openhab/openhabian/blob/master/docs/openhabian-DEBUG.md how to proceed.

these are my settings in etc/network/interfaces

source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet static
address 192.168.x.xxx
netmask 255.255.x.xxx
gateway 192.168.x.xxx

and in etc/dhcpcd.conf

interface eth0
static ip_address=192.168.x.xxx/24
static routers=192.168.x.xxx
static domain_name_servers=192.168.x.xxx

can someone please help me? i just want a fuctional cable connection because i tried the WiFi connection too but its not working properly.
thanks for any hint.

could anyone please share their etc/dhcpcd.conf and etc/network/interfaces. i need to know how the original folders look like. i made many changes in there and right now i cant even access the server via putty. thanks

You may not be using a static IP this way and you must not be messing with config files at all.

Install again from scratch, mind the prerequisites and go read the DEBUG guide if that still does not work.

3 months passed and all my systems are down. i formatted the micro sd card and installed oh3.
i see all my devices on the openhab page and i can make items or links but i cant connect to vscode to use the unbelievable tool called create items from things! i followed a few tutorials, uninstalled and reinstalled vlcode but it cant discover my things on the network!
please anyone point me a way to make openhab work with vsc. i mention that previously with oh2 that was the way i made all my configuration but in oh3 it just wont work.
so i can see everything in openhab interface but i cant make a link with vscode.
please point me a way to start. thanks.

Do you have openHAB vscode plugin installed and configured?

If not then I would start with it.